Diesel itch again- 5.9 vs 6.7 Cummins

Deplorable

Deplorable

Well-Known Member
Joined
Feb 13, 2017
Location
Asheville
Well it’s happening again. I’m convinced my life would be more fulfilling with another diesel tow rig.

I’m struggling to find the right truck. I’ve always wanted a 5.9 due to good reputation, longevity, fuel mileage, simplicity, etc. But having a hard time digesting the extra tax on them. I’m finding some prices are close to newer trucks with similar mileage. That’s what kept me from pulling the trigger thus far. So now considering broadining my search to include 2011 and older 6.7 trucks.

Anything I need to know in comparing these two options? I know 2011 and later have more torque. Does it make sense to keep my search to 2011 and older due to all the emissions additions? Help steer me right!
 
Interior on the 4th gen is nicer than the 3rd gen. also no cracked dash. Before ‘13 for no DEF. Delete the egr and dpf and watch your mileage and power drastically increase. Look outside your local area and don’t be afraid to fly in/drive home for the right deal. Manuals can be found if that’s your flavor but the “factory style” clutches aren’t much good past a stock motor. The newer 6spd autos are pretty stout so not much of a worry there.
 
Manuals are de-tuned from the factory. Autos have higher torque numbers because of the clutch issue @skyhighZJ mentioned above.
 
I can tell you a 2011 6.7 2500, straight rolls with 10k behind it on 37s and gettin 19-21 mpg... (with mods) in other hand I drove a 94 3500 5.9 to Ohio from va 8 hours and avg 20mpg but all stock suspension had exhaust and fuel mod! I’m a 5.9 fan if I had the coin I’d put one behind a 6l80e/4l80e in my burb and love life! Lol
 
C.Berry said:
I can tell you a 2011 6.7 2500, straight rolls with 10k behind it on 37s and gettin 19-21 mpg... (with mods) in other hand I drove a 94 3500 5.9 to Ohio from va 8 hours and avg 20mpg but all stock suspension had exhaust and fuel mod! I’m a 5.9 fan if I had the coin I’d put one behind a 6l80e/4l80e in my burb and love life! Lol
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Is that hand calculated or from the lie o meter. Not that I doubt you but I doubt you.
 
@edward had an 07 6.7 truck with the 6 speed. It was a heck of a truck with all the deletes and a 40HP H&S tow tune. However as mentioned, the clutch had to be upgraded to a South Bend Dual Disk after a while. He averaged over 20Mpg empty and mid teens with a big trailer shaped like a billboard.
Basically, if you’re going to added even just a little power you’ll have to upgrade a clutch or an auto so go with which one you like.
Also, the 6.7 gets you the engine braking which is a real nice feature for loads going down hill.
 
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tsconver said:
Is that hand calculated or from the lie o meter. Not that I doubt you but I doubt you.
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5.9 trip was miles/gas calculated bc I was curious if mileage was any better than a small block 350, the 6.7 was digital little computer/tuner deal so not sure how much it’s telling the truth..
 
C.Berry said:
5.9 trip was miles/gas calculated bc I was curious if mileage was any better than a small block 350, the 6.7 was digital little computer/tuner deal so not sure how much it’s telling the truth..
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The 6.7 is definitely off, mine is consistently 1 mpg high and it varies greatly as reported by others on cumminsforum. So your number is probably high.
 
My 06 gets 26-30 mpg if you look at the overhead. 15-18 if you hand calculate. Nothing else useful to add. Ive never driven 6.7 cummings.
 
tsconver said:
The 6.7 is definitely off, mine is consistently 1 mpg high and it varies greatly as reported by others on cumminsforum. So your number is probably high.
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My 06 Lie-o-meter is off when I'm not towing, says I get 17-18mpg when it's 13-14mpgs. For some reason when you start grossing over 18-19K it becomes accurate, last trip it was only off by .5mpgs.

Now back on topic I would totally look for a new 6spd 6.7 if it were in the cards. Once the 6.7 trucks are deleted they are in the same league as the 5.9 for longevity, mileage, and douche factor:flipoff2:
 
I can't believe I'm gonna say this, I feel like I'm getting old and weak just for saying it, but I love the fact that I can start my DPF/DEF/EGR/SCR equipped truck and not get ran out of the driveway and yard by the diesel smell. My 2008 Ford 6.4 with SCR/cat in place but no DPF was ok, you could definitely tell it was a diesel, but you could stand around it when it was idling without your eyes burning. My 2011 fully deleted Ford 6.7 was really noxious. With the 2012 Ford 6.7 I have now, I left it stock, and have averaged about 17mpg empty hand calc'd, with a best tank of 19.8mpg and a worst tank of 13.1mpg (towing 10k pounds of excavator and trailer in stop and go traffic).
 
Chris_Keziah said:
My 06 Lie-o-meter is off when I'm not towing, says I get 17-18mpg when it's 13-14mpgs. For some reason when you start grossing over 18-19K it becomes accurate, last trip it was only off by .5mpgs.
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The Ford is the opposite, pretty accurate (like within 0.1-0.2mpg) when running empty, and off by 1-1.5mpg when dragging a load around.
 
jeepinmatt said:
I can't believe I'm gonna say this, I feel like I'm getting old and weak just for saying it, but I love the fact that I can start my DPF/DEF/EGR/SCR equipped truck and not get ran out of the driveway and yard by the diesel smell. My 2008 Ford 6.4 with SCR/cat in place but no DPF was ok, you could definitely tell it was a diesel, but you could stand around it when it was idling without your eyes burning. My 2011 fully deleted Ford 6.7 was really noxious. With the 2012 Ford 6.7 I have now, I left it stock, and have averaged about 17mpg empty hand calc'd, with a best tank of 19.8mpg and a worst tank of 13.1mpg (towing 10k pounds of excavator and trailer in stop and go traffic).
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Both mine and my wives are deleted and doesn’t bother at all at idle. Yes they are more noisy but if I wanted quiet I guess I would have bought a civic or the like. But the fumes aren’t noticeable at all?? A difference in the motor, tune, delete??
 
My lie o meter was pretty solid stock. With a box it was off a couple mpg.

I really like the 4th gens... I would entertain a manual without the piss fluid. I like the look the interior and the actual crew cab. I like the 5600 in my 04.5 over the getrag, but that is fixiable, I reckon. The big problem is they cost a fucking fortune. I just do not know if I could come off that much money for a work vehicle. It does not make sense. I will just keep my 3rd gen going
 
I’ve had a 2012 for almost 7 years and it’s a great truck. I have the Longhorn edition which I didn’t really want but it was $12k off the sticker at the time and the saddle leather was extremely nice. It’s nowhere near stock now with turbo swap, deletes, 37’s, upgraded 68rfe transmission, lockers, unlocking hubs, blah blah. It is a monster performing pretty much any task. Get around 16 mixed driving... When I had 35’s, deletes, locking front hubs I could get around 19-20mpg on highway only if I was delicate.

5.9’s are getting tricky to find and most of the time the premium on them is close to the same as a 4th gen. If I were you I’d look at the 2010-2012 trucks in the trim you want. Do a thorough look over. The 68 auto transmissions CAN be finicky but if you get a good one you can do light mods/transmission tuning to make it reliable as long as you don’t run tunes too hot. Sometimes you can find a truck that had head studs /deletes done prior which will save a lot of money (headstuds are close to $1k alone).

Big things to check:
-truck hasn’t popped a head gasket (once you pop you can’t stop)
-transmission is holding good line pressure and shifts well
-lots of used trucks are tuned which is a slippery slope b/c you don’t know how hot they ran it. If it is tuned make sure it comes with the tuner
-owner kept up with fuel filter changes and oil changes

I think the 6.7’s are starting to prove themselves as having the longevity of the 5.9’s. Rarely will you find an issue with the 6.7 rather it’s a problem with the trans or truck around it.
 
C.Berry said:
I can tell you a 2011 6.7 2500, straight rolls with 10k behind it on 37s and gettin 19-21 mpg... (with mods) in other hand I drove a 94 3500 5.9 to Ohio from va 8 hours and avg 20mpg but all stock suspension had exhaust and fuel mod! I’m a 5.9 fan if I had the coin I’d put one behind a 6l80e/4l80e in my burb and love life! Lol
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I would believe those numbers if you were rolling downhill in neutral the entire trip but no gear ratio/transmission combo will give you those #’s with 37’s and pulling weight.
 
usmc42 said:
I would believe those numbers if you were rolling downhill in neutral the entire trip but no gear ratio/transmission combo will give you those #’s with 37’s and pulling weight.
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Well that little screen says 22-24 with no load in slight throttle at 70 mph...lol not sure what kind of tuner deals on it it’s not my truck just hauled with it a bunch of times!
 
Man I wish that screen was right. Would be nice if my truck actually got 23 mpg. Once I calc’d the fuel receipts I wanted to cry a little. Hope all the talk of diesel going up isn’t true.


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skyhighZJ said:
Both mine and my wives are deleted and doesn’t bother at all at idle. Yes they are more noisy but if I wanted quiet I guess I would have bought a civic or the like. But the fumes aren’t noticeable at all?? A difference in the motor, tune, delete??
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Could have been tune related, but my diesel BMW was the same way. It was also tuned and fully deleted. Older VW Passat I had still had the cat on it and was fine. Maybe I'm just more sensitive to whatever emissions the cat takes care of.
 
@jeepinmatt it very well could be tune related. Both of ours run the lowest setting tune just to make the computer happy being deleted. I think I have bumped mine up a couple notches just to see the difference but it’s not the intention to have it a hotrod so I keep them turned down cause they are trucks not race cars so I would suppose the fuel map makes a big difference. My old 12valve on the other hand was a complimentary skeeter killer at idle but had a lot more work under the hood.
 
my 06 with the minimaxx turned all the way up , the only time i smell diesel is if its cold outside. after the grid heater cycles a few times it goes away. (also on stock turbo and injectors 220k miles)

Id like to get into a 4th gen at some point for the interior, i would go ahead and ARP the head even if on a stock tune .
 
RHSCTJ said:
My 06 gets 26-30 mpg if you look at the overhead. 15-18 if you hand calculate. Nothing else useful to add. Ive never driven 6.7 cummings.
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